1. Field of the Invention
The invention pertains to small hermetically sealed, glass encapsulated electrical components and specifically to glass encapsulated components which are sensitive to the heat applied during the hermetic sealing process.
2. Description of the Prior Art
The construction of hermetcally sealed, glass encapsulated small components is known in the prior art. Examples of techniques not useful for temperature sensitive components are disclosed in U.S. Pat. No. 4,446,502. A technique for use with metal film resistors is disclosed in U.S Pat. No. 4,117,589.
A typical commercially available, hermetically sealed, glass encapsulated metal film resistor, available from Mepco/Centralab, Inc., is illustrated in FIG. 1. A finished metal film resistor 10 having axial leads 12 extending from metal end caps 16 has metal discs 14, typically of "Kovar.TM.", welded to each axial lead and spaced apart from the resistor end caps 16. A large diameter glass sleeve 20 is then heat sealed to the discs 14, which discs are spaced apart from the end caps 16 and larger in diameter than said end caps to keep the heat required for the hermetic seal away from the resistive metal film on resistor 10. This prior art device requires elaborate and complicated fabrication techniques to avoid overheating the resistive metal film. Such overheating causes deterioration of the film.
The object of the present invention is to eliminate the potential for overheating while providing a simpler, more reliable and structurally stable device.